1. Field of the Invention
The present invention relates to a substrate processing method, and a storage medium in which is computer-readably stored a program for causing a computer to implement the method, and in particular relates to such a substrate processing method and storage medium for a substrate processing system having an etching apparatus having therein an electrostatic chuck that electrostatically attracts a substrate.
2. Description of the Related Art
A substrate processing system for forming wiring grooves or via holes in a desired pattern using plasma on a front surface of a wafer as a substrate is comprised of a coater that coats a positive type resist onto the front surface of the wafer, an exposing apparatus that subjects a portion of the resist, which has been cured by heating or the like, to light exposure, a developer that uses a developing liquid to remove, from the front surface of the wafer, the resist that has been subjected to the light exposure, thus forming a resist film, an etching apparatus that subjects the front surface of the wafer to etching processing, for example RIE (reactive ion etching) processing, and a washing apparatus that removes the resist film. In recent years, it has become that in such a substrate processing system, from the viewpoint of saving space, the coater and the developer are often integrated together.
The etching apparatus has a housing chamber that houses the wafer and in which plasma is produced, and an electrostatic chuck that is disposed in the housing chamber and electrostatically attracts the wafer thereto while the wafer is being subjected to the etching processing (see, for example, Japanese Laid-open Patent Publication (Kokai) No. 2005-347620).
In the exposing apparatus, the resist on the front surface of the wafer is irradiated with ultraviolet light or the like in a pattern that is reversed with respect to a desired mask pattern. In recent years, as the desired mask pattern has become finer, UV light of a shorter wavelength, for example a wavelength of 193 nm, has come to be used in such an exposing apparatus. If the wavelength is shorter, then the depth of focus is also reduced, and hence the tolerances on the flatness and the inclination of the wafer are reduced. In particular, with such an exposing apparatus, a plurality of pin-like projections support a rear surface of the wafer, and hence the flatness and the inclination of the wafer are greatly affected by scratches, foreign matter etc. on the rear surface of the wafer.
To realize a complex semiconductor device wiring structure or electrode structure on a wafer, the wafer must be subjected to etching processing in the substrate processing system repeatedly, and each time the etching processing is carried out, the wafer is electrostatically attracted to the electrostatic chuck. The surface of the electrostatic chuck is covered with yttria (Y2O3), and hence the rear surface of the attracted wafer, which is made of silicon (Si), may be scratched. Moreover, foreign matter present on the surface of the electrostatic chuck may be transferred onto and thus become attached to the rear surface of the wafer.
Foreign matter attached to the rear surface of a wafer can be removed by wet washing using a washing liquid or the like. However, no method is known for effectively removing scratches from the rear surface of a wafer. There is thus a fear that it may become impossible to maintain the flatness of a wafer within the allowed tolerance due to such scratches on the rear surface of the wafer. Moreover, the yttria or the like may flake off (as dust) due to rubbing between scratches on the rear surface of the wafer and the surface of the electrostatic chuck, forming particles. It is thus necessary to prevent the rear surface of a wafer from being scratched when the wafer is attracted by the electrostatic chuck.